By Noel Randewich SAN FRANCISCO (Reuters) – Nvidia Corp gave a revenue forecast for the current quarter that was shy of Wall Street’s expectations as the graphics chipmaker faces tough competition in tablets and a slow personal computer market. With the personal computer industry losing steam, Nvidia has expanded its graphics chips into mobile devices, but it is meeting stiff competition from Qualcomm Inc and other rivals. In the third quarter, revenue from Nvidia’s Tegra mobile business fell 54 percent and revenue from its PC graphics chip business declined 2 percent. Nvidia’s lighter-than-expected revenue forecast follows other chipmakers that have failed to impress analysts.